Sergeant Major Michael B. Allen enlisted in the U.S. Marine Corps and reported to Marine Corps Recruit Depot, Parris Island, South Carolina in July 2002. In October 2002, Private Allen was meritoriously promoted to the rank of Private First Class. In November 2002, Private First Class Allen reported to Camp Johnson, North Carolina for the Basic Warehouseman School. Upon graduation, he was meritoriously promoted to the rank of Lance Corporal and received the MOS 3051 Warehouse Clerk.
In January 2003, Lance Corporal Allen reported to 2d Supply Battalion, Camp Lejeune, NC where he was selected for the Fleet Assistance Program. He reported to Headquarters and Support Battalion, Provost Marshal's Office, Camp Lejeune, NC where he served as a Military Policeman. In February 2005, Lance Corporal Allen was promoted to the rank of Corporal.
In June 2006, Corporal Allen was promoted to the rank of Sergeant. In August 2006, he attended Military Police school and received the MOS 5811 Military Policeman. He reported to Provost Marshal's Office, Camp Butler Okinawa, Japan where he served as the Platoon Sergeant and Watch Commander for Military Police Districts East and North.
In September 2007, Sergeant Allen reported to Provost Marshal's Office, Camp Lejeune, NC where he served as a patrol supervisor and training NCO.
In July 2009, Sergeant Allen reported to Drill Instructor School Parris Island, SC. After completion of Drill Instructor School, he was assigned to Delta Company, 1st Recruit Training Battalion, where he served as a Drill Instructor and Senior Drill Instructor. In November 2010, Sergeant Allen was promoted to the rank of Staff Sergeant.
In September 2012, Staff Sergeant Allen reported to Provost Marshal's Office, Camp Pendleton, CA where he served as a Platoon Sergeant, Watch Commander, Company Gunnery Sergeant, and deployed in support of the Marine Corps Training Mission United Arab Emirates. In November 2015, Staff Sergeant Allen was promoted to Gunnery Sergeant and served as the Company First Sergeant for Provost Marshal's Office, Camp Pendleton, CA.
In August 2016, Gunnery Sergeant Allen reported to the University of California Los Angeles, Los Angeles, CA where he served as the Assistant Marine Officer Instructor for the Naval Reserve Officers Training Corps (NROTC).
In July 2019, Gunnery Sergeant Allen reported to Provost Marshal's Office, Headquarters and Headquarters Squadron, Marine Corps Air Station Miramar, San Diego, CA. There he served as a Watch Commander and was selected to the rank of First Sergeant during his tour.
In January 2020, First Sergeant Allen reported to 3d Assault Amphibian Battalion, 1st Marine Division, Camp Pendleton, CA. There he served as the Company Senior Enlisted Leader for Company A and deployed in support of the Unit Deployment Program to the Western Pacific.
In December 2021, First Sergeant Allen reported to 1st Intelligence Battalion, I Marine Information Group, Camp Pendleton, CA. There he served as the Company Senior Enlisted Leader for Headquarters Company. In December 2023, he was selected to be the Sergeant Major for Combat Logistics Battalion 7.
Sergeant Major Allen's personal awards include the Navy and Marine Corps Commendation Medal (3rd award) and Navy and Marine Corps Achievement Medal (3rd award).